A conventional ballast control system, such as a system conforming to the Digital Addressable Lighting Interface (DALI) standard as defined in the International Electrotechnical Commission Document, IEC 60929, includes a hardware controller for controlling the ballasts in the system. Typically, the controller is coupled to the ballasts in the system via a single digital serial interface, wherein data is transferred in accordance with DALI protocol. A disadvantage of this single interface is that the bandwidth of the interface limits the amount of message traffic that can reasonably flow between the controller and the ballasts. This can also create delays in response times to commands. Further, a typical DALI compatible ballast control system is limited to 64 ballasts on a communication link. This also creates a disadvantage in that additional controllers are required to accommodate systems having more than 64 ballasts. Yet another disadvantage of a ballast control system having a single controller is that the controller is a single point failure.
That is, if the controller fails, the entire system is down. This is especially burdensome in lighting systems installed at remote locations.
Typically, these systems are configured in a polled configuration requiring a ballast to first receive a transmission from the controller before the ballast can transmit. This can cause response time delays, especially in large systems. Also, these systems do not allow ballasts to be addressed by devices other than the DALI compatible interface, thus limiting the flexibility and size of the control system.
Further, many conventional ballast control systems, such as non-DALI systems, do not allow separate control of individual ballasts or groups of ballasts within the system. Systems that do provide this ability typically require separate control lines for each zone, a dedicated computer, and complicated software to carry out the initial set-up or future rezoning of the system.
Many conventional ballasts include significant analog circuitry to receive and interpret control inputs, to manage the operation of the power circuit and to detect and respond to fault conditions. This analog circuitry requires a large number of parts which increases cost and reduces reliability. In addition, the individual functions performed by this circuitry are often interdependent. This interdependence makes the circuits difficult to design, analyze, modify and test. This further increases the development cost for each ballast design.
These prior art systems lack a simple solution or device for controlling the ballasts and lamps. Thus, an electronic ballast circuit that contains fewer parts to reduce cost and increase reliability, provides flexibility and growth, and does not require a controller dedicated to controlling an entire system is desired.